Silver halide emulsions which are spectrally sensitized and which contain color couplers

ABSTRACT

LIGHT SENSITIVE PHOTOGRAPHIC SILVER HALIDE GELATINE EMULSION CAN BE SENSITIZED OPTICALLY IN THE BLUE RANGE OF SPECTRUM (RANGE OF INHERENT SENSITIVY) BY QUINOLINE MONOAZOCYANNIES, WHEREIN THE SECOND HETEROCYCLIC GROUP IS A QUINOLINE BENZOTHIAZOLE OR BENZOSELENAZOLE GROUP, AND AT LEAST ONE OF THE RING NITROGEN ATOMS CARRIES AN ALKYL GROUP CONTAINING AN ACID SUBSTITUENT.

och-10, 1972 o, RlESTER ETAL 3,597,282

SILVER HALIDE EMULSIONS WHICH ARE SPECTRALLY SENSITIZED AND WHICH CONTAIN COLOR COUPLERS Filed 001'.- 15, 1969 FIG. 7

sbo 550 450 INVENTOR OSKAR RIESTER, BY MARIE HASE.

hired States Patent Patented Oct. 10, 1972 US. Cl. 96-139 1 Claim ABSTRACT OF THE DISCLOSURE Light sensitive photographic silver halide gelatine emulsion can be sensitized optically in the blue range of spectrum (range of inherent sensitivity) by quinoline monoazocyanines, wherein the second heterocyclic group is a quinoline benzothiazole or benzoselenazole group, and at least one of the ring nitrogen atoms carries an alkyl group containing an acid substituent.

The invention relates to silver halide emulsions which contain color couplers and which are spectrally sensitized in the blue region of the spectrum by the addition of monoazacyanines.

It is known that photographic silver halide emulsions can be spectrally sensitized and their range of sensitivity increased beyond their natural sensitivity. For this purpose, sensitizers are added to the emulsions. These sensitizers must fulfill certain conditions if they are to be suitable. Thus, the intensity of sensitization should be as large as possible. The sensitizers, which are often slightly colored, should also be washed out as completely as possible in the course of the photographic process. The sensitizers naturally must not adversely affect the other photographic properties of the materials. Furthermore, their effect should be independent of the other photographic additives such as chemical sensitizers, stabilizers or color couplers.

One special problem is the spectral sensitization of color photographic silver halide emulsions which contain color couplers in dissolved or dispersed form. Most sensitizers, especially the usual polymethine dyes, are insufliciently active in the presence of color couplers.

Another problem is sensitization in the blue region of the spectrum, i.e. the natural sensitivity range of silver halide emulsions.

A certain group of cyanine sensitizers are the so-called azacyanines or cyazines in which methine groups in the methine chain are replaced by nitrogen atoms. Such sensitizers are known per se. They are said to have a particular elfect in silver chloride emulsions. Spectral sensitization of silver bromide emulsions in their natural sensitivity range, however, could not be achieved with such cyanine dyes.

It is an object of the invention to find cyanine dyes which are capable of sensitizing silver halide emulsions which contain color couplers to a sufiicient extent in their natural sensitivity range and which, in addition, meet the usual requirements such as that of being easily removed by washing, etc.

Silver halide emulsions which contain color couplers and the silver halide of which consists mainly of silver bromide or silver chlorobromide have now been found which are spectrally sensitized in the blue region of the spectrum by the addition of quinoline monoazacyanines which contains a quinoline, benzothiazole or benzoselenazole as another heterocyclic residue in which at least one of the ring nitrogen atoms contains an alkyl group with an acid substitutent.

Monoazacyanines of the following formula are especially suitable:

R and R represent a hydrogen atom or an alkyl or alkoxy group preferably containing 1 to 3 carbon atoms or a halogen atom such as a fluorine, chlorine or bromine atom, or a trifluoromethyl or phenyl group or a condensed benzene ring;

R and R" represent hydrogen or an aliphatic saturated or unsaturated radical preferably containing up to 4 carbon atoms, which may be substituted, in particular in the w-position with a hydroxyl, alkoxy, sulfo, sulfato, sulfoalkoxy, carboxyl, sulfamide, sulfamyl, N-sulfonylsulfamyl, N-sulfonylcarbamyl or phosphonic acid, at least one of the two groups R and R" containing an acid substituent; and represents a vinylene radical or a selenium or sulfur atom.

The azacyanines for use according to the invention may, of course, also be present in the form of other mesomeric structures since the positive charge of the dye obtained by quaternization generally cannot be considered as being localized. The actual molecular state in therefore more accurately represented by writing the above formula as follows:

Z R l I II Compounds of the following formula (which are here shown as betaines), for example, are suitable:

G MS OaNCO OH;

' TABLEContinued TABLE-Cntinued H Sens. Sens. max. m max. in, S (0 5 1i fl) l \e/ N N r 1? 9 (5H! CH; (011938 Ol (CHzhSOl 10 4 456 (6).-.-.-.. 454 O1 \e/ N I 53/ WN/ N 5 5.11. nmsm (3H 0 9 18 471 ms 11.00- x f OCH: (1);"--. 447 T i'i 20 hm (inn). s m9 N 5H so 9 l a i f The sensitizers for use according to the invention are prepared by known methods. These are described in detail 441 below for some of the above-mentioned compounds.

i I COMPOUND 3 01 \fil N N 1st stage: '1-methyl-2-(benzothiazol-2-ylimino)-1,2-

T E dihydroquinoline CHZOHPC 3d 2.8 g. of Z-aminobenzothiazole and 6.4 g. of l-methyl-Z- (9) 452 methyltio-quinolinium-methylsulfate are together heated S I on an oil bath at a temperature of 160 C. for 50 m1nutes. The reaction temperature is 165 C. This tempera- C N ture drops after about 20 minutes. The reaction product is g N/ cooled and triturated with 20 ml. of water until the whole 6 6 s 0, product has crystallized. The product, separated by suction filtration and washed with water, is then dissolved in 70 ml. (10)----" 450 of methanol, treated with active charcoal, filtered and evaporated to half its volume. The solution is made acid f 40 with glacial acetic acid and precipitated with 4 ml. of 50% g N N/ Y sodium perchlorate solution. The product, separated by A e suction filtration, is washed with water and then with n- (cHmsoa propanol and finally boiled twice with 20 ml. portions of (11) i 452 benzene. The perchlorate obtained is introduced into 30 j r ml. of water and made slightly alkaline with a 10% soda solution and thoroughly stirred several times with ml. Q/ 7 portions of benzene. The benzene solution is separated oif J} g e and concentrated by evaporation in vacuo.

Hmso' The product obtained is triturated with 10 ml. of ace- (12) 448 tone, removed by suction filtration and washed with cyclohexanone. M.P. 174 0.

' 2nd stage :Q N O 0 6 g. of the product described above and 1 g. of propane 53mg 019006113 55 sultone are heated at an oil bath temperature of 170 C. for 20 minutes. The reaction temperature is also 170 C. .(13) 452 The product is cooled in ice water and triturated with acetone in a trituration dish. The acetone is decanated off and the dye is triturated with water, then removed by suction \gi N I filtration and washed with acetone. The dye is dissolved in 5 6 e 30 ml. of methanol, filtered and, after the addition of 1 g. Hmso potassium iodide, concentrated by evaporation to one- (14) 452 third its volume. The dye is left to crystallize, removed by suction filtration, redissolved in 20 ml. of methanol, f i filtered, concentrated by evaporation to one-third of its v volume, removed by suction filtration and boiled with ace- N tone M.P. 290 C. 1.5 g. of dye can also be obtained from ormism inn-or an, the mother liquor.

H COMPOUND 7 (1'5) 454 5 g. of 2-methylthio-3-methyl-5-chloro-benzothiazolium methyl sulfate, 3 g. of Z-aminoquinoline, 40 cc. of pyridine, and 10 cc. of tn'ethylamine were heated to boiling under N reflux for 4 hours. The reaction mixture was then poured immsoz into 200 cc. of water and the product which solidifies on s cooling was removed by suction filtration. The product was purified by dissolving it in 50 cc. of chloroform and treating the solution with charcoal and then adding 50 cc. of methanol. After cooling, the product which crystallizes out was removed by suction filtration. 1.2 g. of the product described above were heated with 0.6- g. of propane sultone for 20 minutes in an oil bath at a temperature of 170 C. The melt was dissolved in 25 cc. of alcohol and filtered, and 25 cc. of water were added. After cooling, the crystallized product was removed by suction filtration. The compound does not melt below 300 C.

COMPOUND 8 0.3 g. of l-methyl-2-(benzothiazol-2-ylimino)-1,2-dihydroquinoline (see Dye No. 3, 1st stage) and 0.3 g. of fl-iodopropionic acid are heated on an oil bath at a temperature of 170 C. for 30 minutes. The product is cooled, triturated with a little water and removed by suction filtration. The crude dye is treated with a little 1% soda solution (the solution must remain slightly alkaline) and thoroughly stirred several times with benzene. The solution in benzene must no longer be yellow. The dye is dissolved warm in 10 ml. of water, some calcium nitrate solution is added, and the reaction mixture is filtered hot. It is left to crystallize, filtered with suction and washed with a little water and then dried in a drying cupboard. M.P. 144 C.

COMPOUND 11 1st stage (EMT/t) 7 g. of the above product are reacted with g. of propane sultone by heating on a steam bath. The temperature rises to about 130 C. The reaction product is triturated with acetone, removed by suction filtration and recrystallized from 60 cc. of 50% alcohol. M.P. 192 to 194 C.

DYE 'NO. 17

1st stage JIHB 35 g. of 1-ethyl-2-methylthio 6 chloro-quinolinium methyl sulfate, 14 g. of Z-aminoquinoline and 60 cc. of isoquinoline are heated on an oil bath at a temperature of 170 C. for 20 minutes. The reaction mixture was then dissolved in 600 cc. of water and treated with 60 cc. of conc.'hydrochloric acid (1.19). After cooling, the crystalline product was removed by suction filtration, slurried with 400 cc. of water and made alkaline with 80 cc. of 45% sodium hydroxide solution and then heated for a short time on a steam bath. A smeary product separated out. After the alkaline liquid had been poured off, this product was triturated twice with water, and it solidified. It was removed by suction filtration and recrystallized from 200 cc. of acetone. This product is sufficiently pure for working up. M.P. 2'19 to 221 C.

2nd stage 6.6 g. of the substance described above and 2.8 g. of propane sultone were heated on a steam bath. The reaction temperature rises to C. The melt was then dissolved in 50 cc. of methanol. Charcoal was added to the solution, the solution was filtered and the product was precipitated with cc. of water and, after cooling, it was removed by suction filtration. It was purified by recrystallizing it from 100 cc. of 501% methanol.

The compound does not melt below 300 C.

The monoazacyanines for use according to the invention can be washed out very easily. Completely colorless layers are obtained after processing, which is of utmost importance especially when using the substances for photographic materials on paper as a layer support.

The action of the monoazacyanines is practically independent of the presence of color couplers of any structure or of other additives.

The intensity of sensitization in the blue region of the spectrum is excellent. The selectivity, i.e. the ratio of blue sensitivity to yellow sensitivity is thus greatly improved in favour of the former. By means of the sensitizers according to the invention, the sensitization maximum of the blue sensitive layer of a color photographic printing material can be shifted into the absorption maximum of that layer of the color photographic copying material which contains the yellow dye. A considerably improved separation of color and thereby improved color reproduction are thereby achieved by means of the monoazacyanines for use according to the invention.

The silver halide emulsions according to the invention are preferably only blue sensitive and contain yellow couplers, particularly of the benzoyl acetarylide type. The great effectiveness of the sensitizers for use according to the invention is, however, completely preserved even in the presence of other color couplers, e.g. magenta couplers of the pyrazolone type or cyan couplers of the a-naphthole series. The structure of the color couplers is obviously not critical. Useful color couplers have been described, for example, in the publication by W. Pelz, Mitteilungen aus den Forschungslaboratorien der Agfa, vol. III, 1961, pp. 111 et seq.

The emulsions according to the invention may also contain colored color couplers, e.g. so-called azo masking couplers, dyes for the silver dye bleaching process or dyes which have the properties of developers as a result of suitable substituents.

The sensitizing dyes according to the invention may be used in any silver halide emulsions. Suitable silver halides are silver chloride, silver bromide or mixtures thereof, if desired, with a small silver iodide content of up to 10 mols percent. The silver halides may be dispersed in the usual hydrophilic compounds such as carboxymethyl cellulose, polyvinyl alcohol, polyvinyl pyrrolidone, alginic acid and its salts, esters or amides, or preferably, in gelatin.

Preferably are used such emulsions the inherent sensitivity of which is within the blue region of the spectrum.

The sensitizing dyes for use according to the present invention are preferably added to the photographic emulsion after chemical ripening and before casting. The methods used for this are generally known to the expert. Sensitizing dyes are generally incorporated into the emulsion in the form of solutions. The solvents must, of course, be compatible with gelatine and must not have any undesirable influence on the photographic properties of the emulsion. The quantity of sensitizing dye added may vary within wide limits, e.g. between 2 and 200 mg, preferably between 10 and 60 mg. per kg. of silver halide emulsion. The concentration of dye may be adapted to the particular requirements depending on the type of emulsion, the desired sensitization effect, etc. The most suitable concentration for any given emulsion can be easily determined by the usual tests employed in photographic practice.

The emulsions may also contain chemical sensitizers, e.g. reducing agents'such as stannous salts, polyamines such as diethylene triamine, and sulfur compounds such as described in US. patent specification 1,574,944. The above-mentioned emulsions may also contain salts of noble metals such as of ruthenium, rhodium, palladium, iridium, platinum or gold for chemical sensitization, as described in the article by R. Koslowsky, Z. Wiss. Phot., 46, 65-72 (1951).

The emulsions may also contain polyalkylene, oxides, especially polyethylene oxide and derivatives thereof, as chemical sensitizers.

The emulsions according to the invention may contain the usual stabilizers, e.g. homopolar or salt-type compounds'of mercury with aromatic or heterocyclic rings, such as mercaptotriazoles, simple mercury salts, sulfonium mercury double salts and other mercury compounds. Azaindenes, especially tetraand penta-azaindenes and in particular thosewhich are substituted with hydroxyl or amino groups are also suitable as stabilizers. Such compounds are described in the article by Birr, Z. Wiss. Phot., 47, 2-58 (1952). Other suitable stabilizers are, inter alia, heterocyclic mercapto compounds, e.g. phenylmercaptotetrazole, quaternary benzothiazole derivatives, benzotriazole and the like.

The emulsions may be hardened in the usual manner, for example with formaldehyde or halogen-substitued aldehydes which contain a carboxyl group, such as mucobromic acid,diketones, methanesulfonic acid esters, dialdehydes and the like.

EXAMPLE A silver iodobromide gelatine emulsion which contains 1 mol percent of silver iodide and a total of 19.2 g. of silver per literin the form of silver halide is divided into several parts.

The color couplers indicated below are added to the individual samples. A portion of these samples is then optically sensitized by the addition of 45 mg. per liter of sensitizer Ill. The emulsions of the individual pairs of samples with and without sensitizer are then tested for blue sensitivity to yellow sensitivity, using the usual sensitometric methods.

The spectral sensitivity curve of the unsensitized emulsion is represented in the appended FIG. 1, that of the TABLE [Ratio of blue to yellow sensitivity] Without With None sensitizer sensitizer The figures in the two right-hand columns denote stages of a {/2 test wedge in which the first visible stage is counted. The blue sensitivity is measured by exposure behind a filter with a transmittance range of 415 to 480 mg, the yellow sensitivity behind a filter which is transparent above 480 mg.

The intensity of sensitization is fully preserved even in the presence of color couplers (marked I-maximum). The sensitivity is concentrated in the blue violet region of the spectrum around 450 mg, i.e. the blue sensitivity is increased while the yellow sensitivity drops. This selectivity is particularly important for color layers in obtaining improved color separation. Other sensitizers for use according to the invention yield similar results.

What is claimed is:

1. In a color photographic light sensitive material having at least one layer containing a silver bromide emulsion in which the silver bromide emulsion is spectrally sensitized with a dye the improvement according to which the silver bromide emulsion contains a monoazacyanine of the following formula in which R and R'" represent hydrogen, an alkyl or alkoxy group, a halogen atom, trifluoromethyl, a phenyl group, or a condensed benzene ring;

R'and R represent hydrogen, an aliphatic saturated or unsaturated radical containing up to 4 carbon atoms which may be substituted with' hydroxyl, alkoxy, sulfo, sulfoalkoxy, sulfato, carboxyl, sulfamide, sulfamyl, N-sulfo'nylsulfamyl, N-sulfonylcarbamyl or phosphonic acid groups, at least one of the two groups R' and R" containing an acid substituent; and

Z represents .a vinylene radical or a selenium or sulfur atom in an amount that spectrally sensitizes the bromide emulsion in the blue region of the natural sensitivity range of the silver bromide emulsion.

References Cited 5 UNITED STATES PATENTS 10 3,411,916 11/1968 Brooker et a1. 96102 3,519,430 7/1970 Heseltine et a1. 96102 FOREIGN PATENTS 447,109 5/1936 Great Britain.

ROBERT F. BURNETT, Primary Examiner l1 22232 G. w. MOXON II, Asslstant Examiner Derbyshire 96--102 Thompson 96-102 10 96 100 Sprague 96102 

